In a use in which rigidity is required against a moment load, such as a rolling bearing used in an industrial robot, an angular ball bearing or a tapered roller bearing is generally pressurized to use. In a case in which high rigidity is required, the tapered rolling bearing having a large load capacity in the same size is rather used. In recent years, the moment load against a size of the bearing becomes larger, and therefore necessary rigidity has been increased. Further, a space for the bearing becomes smaller due to miniaturization of a whole of an apparatus. That is, a tapered roller bearing having a small size and a high load capacity is desired.
A general tapered rolling bearing according to a conventional technique is described with reference to FIG. 5. As shown in FIG. 5, a tapered roller bearing 11 is provided with an inner ring 12 having a tapered raceway surface 12a on an outer circumference surface, an outer ring 13 having tapered raceway surface 13a on an inner circumferential surface, a plurality of tapered rollers 14 which rolls between the raceway surface 12a of the inner ring 12 and the raceway surface 13a of the outer ring 13, and a retainer 15 which retains each tapered rollers 14 in each pocket portion in a rolling manner. The retainer 15 is formed by joining a large diameter ring portion 15a and a small diameter ring portion 15b by a plurality of column portions 15c. The retainer 15 houses the tapered roller 14 in a pocket portion 16 between the column portions 15c adjacent to each other. A large flange 12b is integrally formed on a large diameter side end portion of the inner ring 12 and a small flange 12c is integrally formed on a small diameter side end portion of the inner ring 12, and thereby the tapered roller 14 and the retainer 15 are prevented from dropping off from the inner ring 12. The inner ring in the tapered roller bearing has the tapered raceway surface, and thereby the inner ring includes a small side and a large side when seen from an axial direction. “The small flange” is a flange arranged on the small diameter side end portion, and “the large flange” is a flange arranged on the large diameter side end portion.
Relating to such a tapered roller bearing, in Patent Document 1, a construction in which the raceway surface of the inner ring is continued until the small diameter side end portion of the inner ring and thereby the raceway surface is ensured, is proposed. Patent Document 1 discloses that the tapered roller, the inner ring, and the retainer are separated by continuing the raceway surface of the inner ring until the small diameter side end portion, however the tapered roller and the retainer can be integrated by modifying a shape of the retainer. Further, in Patent Document 1 and Patent Document 2, as a manufacturing method of the retainer in which the tapered roller and the retainer are integrated, it is disclosed that the retainer is formed by means of injection molding by using two molding dies in an axial direction (axial draw).
The retainer in the tapered roller bearing according to Patent Document 1 is described with reference to FIG. 6. As shown in FIG. 6, a retainer 21 is formed to retain a tapered roller (not shown) in a pocket portion 22. In order to prevent the tapered roller from dropping off from the pocket portion 22 in assembling, tapered surfaces 24, 25 are formed at an inner diameter side and an outer diameter side of a column portion 23, respectively. The tapered surface 24 at the inner diameter side and the tapered surface 25 at the outer diameter side are diagonally arranged to each other on one surface of the column portion 23. Further, a groove 26 is formed along a molding die dividing line, and thereby even if a burr is generated between the molding dies after molding, the interruption of the burr against the tapered roller is prevented.